Hounsfield unit value has null effect on thyroid nodules at 18F-FDG PET/CT scans

Abstract

Objectives: Detection rate of thyroid nodules is increasing with the use of new imaging modalities, especially in screening for malignancies. Positron emission tomography/computed tomography (PET/ CT)-positive thyroid nodules should be differentiated for malignancy to avoid unnecessary operations and further follow-up. Most trials evaluate the role of SUV max , but there is no definitive information about the utility of Hounsfield unit (HU) values for prediction of malignancy. This study aimed to evaluate the HU values beside SUV max for detecting malignancy risk of PET/CT-positive thyroid nodules. Subjects and methods: Results of 98 cancer patients who had fine needle aspiration biopsy (FNAB) for thyroid nodules detected on PET/CT between January 2011 and December 2015 were assessed. The FNABs and surgical pathological results were recorded. Results: FNABs revealed benign results in 32 patients (32.7%), malignant in 18 (18.4%), non-diagnostic in 20 (20.4%), and indeterminate in 28 (28.5%). Twenty-four patients underwent thyroidectomy. The mean HU values were not significantly different in benign and malignant nodules (p = 0.73). However, the mean SUV max was significantly higher (p < 0.001) in malignant ones. Area under curve (AUC) was 0.824 for SUV max ; the cutoff value was over 5.55 (p < 0.001), with 80% sensitivity, 84.5% specificity. Conclusions: Our current study demonstrated that HU value does not add any additional valuable information for discriminating between malignant and benign thyroid nodules. We also defined a SUV max cutoff value of 5.55 for malignant potential of thyroid nodules detected on PET/CT.

Characteristics of malignant thyroid lesions on [18F] fluorodeoxyglucose (FDG)-Positron emission tomography (PET)/Computed tomography (CT)

“…Few studies have addressed the utilization of HU values on LDCT of F-18 FDG PET/CT for prediction of malignant TI [14,19,20,60,61]. In the current study, both benign and malignant lesions are relatively hypodense compared to normal thyroid gland density of control group.…”

“…Pérez et al [49] reported SUVmax 4.2 as the optimal threshold to discriminate malignancy with an area under receiver-operating characteristic curve of 0.76 (95 % confidence interval, 0.60-0.90). Haydardedeoglu et al [19] reported cut-off value for SUVmax to be 5.55. Some of previous publications reported a statistically significant difference between SUVmax of benign lesions and the value of malignant ones [4,14,[50][51][52][53], whereas other studies did not [5,18,32,46].…”

“…To avoid patient anxiety, additional costs, and potential risks associated with further investigation and surgical management of 18 F-FDG-avid TI, an additional diagnostic tool besides SUVmax is required [19]. The use of Hounsfield unit (HU) values on the low-dose CT (LDCT) of F-18 FDG PET/CT to discriminate between benign and malignant TI has been suggested.…”

“…The use of Hounsfield unit (HU) values on the low-dose CT (LDCT) of F-18 FDG PET/CT to discriminate between benign and malignant TI has been suggested. However, only few studies have addressed the utility of HU values for prediction of malignant TI [14,19,20].…”

Support Vector Machine Parameter Optimization for Positron Emission Tomography Images for Estimation of Recurrent Laryngeal Nerve Injury with Thyroid Nodules

“…Some research results showed that the benign and malignant TN had a reliable correlation with CT image characteristics [13,14]. Moreover, PET/CT was used in more and more studies to diagnose patients, and the semiquantitative index SUV max could be applied for the diagnosis and evaluation of benign and malignant nodules [15].…”